In the context of demands for peak shift (i.e., load balancing) of electric power supply in the society as a whole and economical efficiency in consumer sites, there are proposed electric power supply systems including storage batteries interconnected to commercial electric power systems (hereinafter, simply called the systems) to store electric power supplied from the systems for later use. Such electric power supply systems may be provided in households, commercial and industrial facilities, and others to store, in the storage batteries, electric power purchased from the electric power systems during a certain time period, such as midnight, when the cost of electric power is relatively low and to supply the electric power to electric power loads located in the households or premises by discharging the storage batteries during a certain time period, such as daytime.
For instance, Patent Literature 1 describes an electric power supply control device configured to supply electric power from a storage battery when an estimated electric energy generation is less than an estimated electric energy demand in an electric power supply system connected to a system and an electric power generator.